This invention discloses the method of heating a part of a first underground deposit of coal or lignite by magnetic induction under controlled temperature and pressure, to recover hydrocarbon fluids, with subsequent combustion of the remaining carbon and air and steam to produce a combustible gas used to generate electrical power. The electrical power is partly used to heat another part of the first deposit from which hydrocarbon fluids have been recovered, and is partly transmitted to second underground deposits of oil shale, tar sand or heavy ol, where it is used to heat the second deposits by magnetic induction, under controlled temperatures and pressures, to recover hydrocarbons in fluid form.
In the prior art the multiple-site operation described above does not use controlled temperatures and pressures at each deposit.